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Natural Gas

Natural gas is a fossil fuel extracted from oil wells. It is composed of at least 85% methane; other hydrocarbons and water vapor make up the rest. A small percentage of natural gas is extracted from renewable sources (some landfills and water treatment facilities).

Currently in the US, one-tenth of one percent of natural gas is used as a transportation fuel.

photo by Jayesh Nair

Properties

Gas, non-toxic, non-corrosive, non-carcinogenic.

Production

Natural gas is first separated from free liquids (crude oil, water, etc), then processed according to certain pipeline quality specifications by a dehydration plant, a gas processing plant, and a gas sweetening plant.

CO2 Emissions

Fuel Blends

It can be blended with hydrogen to create hydrogen/natural gas blends (HCNG), a blend with fewer nitrogen oxide emissions than natural gas.

Infrastructure

Natural gas already uses the existing utility/pipeline system. Currently there are hundreds of fueling stations operational across the US, but most only dispense compressed natural gas (CNG). Stations dispensing liquefied natural gas (LNG) are not as prevalent.

The U.S. Environmental Protection Agency considers the Civic GX the “cleanest-burning internal-combustion vehicle on the planet.”

Compared to Gasoline

The fuel economy of a vehicle powered by compressed natural gas (CNG) is effectively equal to a vehicle powered by gasoline with considerably lower pollutant emissions.

Advantages

It is a high octane, clean-burning fuel which doesn’t threaten soil, surface water, or groundwater.

It’s a well-established energy source, currently providing the US with one quarter of its energy needs, and it is available in massive amounts domestically.

Disadvantages

Much of it is a non-renewable resource.

Its hydrocarbon emissions are far lower than gasoline, with the exception of methane, in which case they’re higher.

On-board vehicle storage is an issue. In order to achieve a reasonable driving range, CNG needs to be stored at a very high pressure, around 3,600 pounds per square inch. LNG attempts to solve this space problem, but in order to turn the gas to a liquid, it must be cooled to -260°F (-162°C), a temperature so cold that it requires its own special on-board storage.

The Future

The future of natural gas vehicles may already be here. The 2007 Honda Civic GX is a dedicated natural-gas vehicle, meaning it runs purely on natural gas. It is neither a hybrid, flexible-fuel, or bi-fuel vehicle. Its engine emissions are almost zero, and the vehicle’s range is approximately 170 miles on a full tank of natural gas. The U.S. Environmental Protection Agency considers the Civic GX the “cleanest-burning internal-combustion vehicle on the planet.”

The future of natural gas also lies with its hydrogen-to-carbon ratio—the highest of any known energy source. This ratio explains why natural gas is the top source of commercial hydrogen in the US. It also suggests how natural gas might serve as the ideal transition fuel for the introduction of hydrogen and a hydrogen economy: As a gas, it already has an in-place infrastructure that could possibly be converted into one for hydrogen.

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